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Questions of morphological study addressing living and fossil organisms are briefly discussed. The importance of ontogenetic patterns and processes in evolutionary biology are viewed on the background of three special problems of cephalopod morphology: the reproductive system of octopods, the lower beaks of coleoids and ammonites, and the arm crown of the coleoids. <...>
Cephalopods are diverse, highly developed molluscs capable of swimming and jet propulsion. These animals are an important component of present-day marine ecosystems throughout the world and comprise approximately 900 species. They also have an extraordinary fossil record, extending back to the Cambrian Period, with as many as 10,000 extinct species. Throughout their long history, they have experienced spectacular radiations and near-total extinctions. Because of their superb fossil record, they also serve as ideal index fossils to subdivide geologic time. This book touches on many of these themes, and it treats both fossil and present-day cephalopods. The chapters are outgrowths of presentations at the Sixth International Symposium “Cephalopods – Present and Past,” at the University of Arkansas in Fayetteville, September 16–19, 2004. The Symposium was organized principally by Walter L. Manger of the Department of Geology, University of Arkansas. The editors gratefully acknowledge Walter for his terrific job in putting together this symposium and for making it such an intellectual, and social, success. Other publications related to this Symposium include the abstract volume, assembled by W. L. Manger, and two fieldtrip guidebooks, one written by W. L. Manger, and the other by R. H. Mapes. <...>
This book is intended to be a concise and comprehensive coverage of the key ceramic and glass materials used in modern technology. A group of international experts have contributed a wide ranging set of chapters that literally covers this field from A (Chap. 1) to Z (Chap. 10). Each chapter focuses on the structure–property relationships for these important materials and expands our understanding of their nature by simultaneously discussing the technology of their processing methods. In each case, the resulting understanding of the contemporary applications of the materials provides insights as to their future role in twenty-first century engineering and technology <...>
This work could not even have been attempted, much less completed, without the help of numerous friends and colleagues. In roughly chronological order (my sample collecting formally began in 1985), I extend my sincerest thanks to the following people, beginning with those based in Ohio institutions: N’omi Greber and David Brose, then at the Cleveland Museum of Natural History; Olaf Prufer and Mark Seeman at Kent State University;
The Jerónimo sedimentary rock-hosted disseminated Au deposit is located within the Potrerillos district of the Atacama region of northern Chile, east of the Potrerillos porphyry Cu-Mo and El Hueso high-sulfidation Au deposits. Prior to development, the Jerónimo deposit contained a resource of approximately 16.5 million metric tons (Mt) at 6.0 g/t Au. Production began in the oxidized, nonrefractory portion of the deposit in 1997 and terminated in 2002. During that time, approximately 1.5 Mt at 6.8 g/t Au was mined by underground room-and-pillar methods, from which a total of approximately 220,000 oz of Au was recovered by heap-leach cyanidation.
The geology of northwestern Mexico is complex and is similar in many respects to that of southeastern California and southern Arizona. The region (Fig. 1), typical of the southern basin-and-range physiographic province of which it is a part, is characterized by elongate, northwest-trending ranges separated by wide alluvial valleys. Basement rocks in the area include Precambrian gneisses, metamorphosed andes-ites, and granites. These rocks are overlain by younger Proterozoic quartzites and limestones, Paleozoic and Mesozoic carbonate rocks, and Mesozoic volcanic, clastic, and carbonate sedimentary rocks. Mesozoic plutonic rocks and Tertiary extrusive and intrusive rocks related to volcanic activity of the Sierra Madre Occidental are widely distributed. Broad areas are underlain by plutonic and associated volcanic rocks of the Sonora-Sinaloabatholith of Cretaceous to early Tertiary (Laramide) age. The outcrop areas of the plutonic rocks are smaller in northwestern Sonora, west of Magdalena de Kino where many of the gold deposits are concentrated, than they are farther to the east and south (Fig. 2).
We would like to extend our appreciation to Morris and Tooker for their comments, discussion, and additional information that they provide pertaining to the geologic environment of the Mercur gold district, Utah. Their review of the characteristics of the Sevier orogenic belt are particularly relevant; however, such characteristics must be interpreted within the context of the additional geologic events of the region, which include the Jurassic compressional event that has been described from northern Utah and western Nevada. For this purpose, we offer the following reply.
Morris and Tooker have two main points of disagreement with our paper. First, they find the range of K-Ar ages we reported as disturbing and indicate that they date neither tectonic, hydrothermal, nor gold mineralization events; and second, they contend that all mineralized structures at Mercur must be younger than Late Cretaceous in age.
Groundwater is a vital resource in steadily increasing demand by man, but man threatens its quality and mishandles the available quantity. In order to properly manage the resource, we have to study it in detail, recognize its properties, and understand its dynamics—in large-scale regions as well as in every locally studied system. Chemical and isotopic hydrology are tailored to these challenges, and the hydrochemist has a key role as a consultant to the groundwater developers and managers, decision-makers, and environmental quality authorities
Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ~ Rb (-~ Tl) = Ba(= W) > Th > U ~ Nb = Ta ~ K > La > Ce = Pb > Pr (~ Mo) ~- Sr > P --~ Nd (> F) > Zr = Hf = Sm > Eu ~ Sn (~ Sb) ~ Ti > Dy ~ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (~<1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (~<2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.
